Well, what ever you get, be safe with it. You can still kill someone with some of the higher power models if you hit a vital point. Safety glasses, gun rules, etc apply for air guns as well.
As for the guns, most things under $75 will not have a decent velocity, so long range shooting will be difficult. Look for something with as high fps as you can get.
Here are a bunch of reviews
http://www.airguns.net/reviews.html
Here is an interesting Kit.
http://www.pyramydair.com/cgi-bin/model.pl?model_id=338
From here
http://www.pyramydair.com/cgi-bin/sh...md_search=Show
Have fun and be safe.